The present application is based on and claims priority to Japanese Patent Application No. 11-170731, which was filed on Jun. 17, 1999, the entire contents of which are hereby expressly incorporated by reference. The entire contents of Japanese Patent Application No. 11-75968, which was filed on Mar. 19, 1999, are also hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to a lubrication system of an internal combustion engine. More particularly, the present invention relates to a lubrication system of a small watercraft engine that powers a water propulsion device.
2. Description of Related Art
As personal watercraft have become popular, they have become increasingly fast. Today, personal watercrafts are capable of speeds greater than 60 mph. To attain such speeds, personal watercrafts are driven by high power output motors.
Typically, two-cycle engines are used in personal watercraft because two-cycle engines have a fairly high power to weight ratio. One disadvantage of two-cycle engines, however, is that they produce relatively high emissions. In particular, large amounts of carbon monoxide and hydrocarbons are produced during operation of the engine. When steps are taken to reduce these emissions, other undesirable consequences typically result, such as an increase in the weight of the engine, the cost of manufacture, and/or the reduction of power.
It has been suggested that four-cycle engines replace two-cycle engines in personal watercraft. Four-cycle engines typically produce less hydrocarbon emissions than two-cycle engines while still producing a relatively high power output. However, adapting four-cycle engines for use in personal watercraft has its own engineering and technical challenges due to, at least in part, the limited space available within the hull of a personal watercraft.
Thus, there exists a need for a lubrication system that does not occupy an excessive amount of space within the engine compartment of a watercraft.
Thus, according to one aspect of the present invention, a watercraft comprises a hull defining an engine compartment. An internal combustion engine is supported within the engine compartment. The engine includes an engine body, at least one lubricant gallery therein, and has an output shaft. A propulsion device is supported by the hull and driven by the internal combustion engine. At least one lubricant pump assembly includes a pump shaft that is co-axially aligned with and driven by the output shaft of the engine so as to circulate lubricant through the engine body. A lubricant reservoir is arranged above the lubricant pump.
By disposing the pump shaft of the pump assembly co-axially with the output shaft of the engine and mounting the lubricant reservoir above the pump assembly, the present lubrication system better utilizes the limited space available within the engine compartment of small watercraft. Preferably, the lubricant reservoir is mounted directly to the engine body. As such, the lines extending between the lubricant reservoir and the engine body for delivering lubricant can be made shorter, thus occupying less space and requiring shorter lengths of lubricant lines which can reduce raw material costs. Additionally, servicing of the engine is also further simplified. For example, when an engine must be removed from the engine compartment of a small watercraft, there may be many components that must be disconnected from the engine body before the engine body can be removed from the engine compartment. By connecting the lubricant reservoir directly to the engine body, the engine and the lubricant reservoir, depending on the size of the access opening of the particular watercraft, can be lifted out of the engine compartment together.
Also preferably, the lubricant reservoir is mounted directly to the pump assembly. As such, the lubrication occupies even less space and further reduces costs associated with raw materials used for lubricant lines.
According to another aspect of the present invention, a watercraft includes a hull defining an engine compartment, an internal combustion engine supported within the engine compartment, the engine having an engine body, at least one lubricant gallery therein, and having an output shaft, a propulsion device supported by the hull and driven by the internal combustion engine, a lubricant reservoir, and at least one lubricant pump assembly driven by the output shaft and configured to circulate lubricant between the lubricant reservoir and the engine body, the lubricant reservoir comprising an upper portion and a separate lower portion connected so as to define at least a portion of the lubricant reservoir.
By constructing the lubricant reservoir from two separate portions, the construction and assembly of the reservoir is simplified. For example, the lubricant reservoir preferably includes a vapor separator therein, which can be constructed from a baffle assembly. By constructing the lubricant reservoir from two separate portions, the baffle assembly can be easily installed into the lubricant reservoir, thus simplifying the manufacture of the engine.